Oxidative and endoplasmic reticulum stress in absence epilepsy

为研究失神癫痫（lethargic，Ih/Ih）小鼠脑内内质网（endoplasmic reticulum，ER）应激诱导的细胞死亡的特点，建立了一种失神癫痫的遗传模型，比较了Ih/Ih小鼠和对照小鼠脑内ER应激诱导的细胞死亡的相关通路。昏睡小鼠丘脑湿重低于对照组。丘脑在失神癫痫中起着重要的作用。嗜睡小鼠丘脑中葡萄糖调节蛋白（GRP）78、ER分子伴侣的含量、c-jun-N-末端激酶（JNK）活性、磷酸化JNK/JNK比值均高于对照组。为了阐明细胞损伤途径的机制，本研究在小鼠海马细胞系HT 22中研究了内质网应激（衣霉素; TM）和氧化应激（H_2O_2和4-羟基-2-壬烯醛; HNE）诱导的细胞损伤途径。TM、H_2O_2和HNE处理后，细胞活力呈时间和浓度依赖性下降。TM可诱导GADD 153/C/EBP同源蛋白（CHOP）表达。相反，caspase-12，ER应激特异性caspase的表达，不受TM的影响。在H_2O_2处理的细胞中，DJ-1和核因子-kB（NF-kB）亚单位的免疫反应性在细胞核中显著增加。H_2O_2还可引起细胞内Ca^<2+>浓度的升高，而Ca^<2+>通道抑制剂氯化钴则可抑制H_2O_2引起的细胞死亡。HNE处理的细胞中没有上述现象，但HNE加合物蛋白在HNE处理后形成，而在H_2O_2处理后没有形成。

In order to characterize absence epilepsy-associated increases in endoplasmic reticulum (ER) stress-induced celluar damege in lethargic(Ih/Ih)mice, a genetic model of absence epilepsy, responsible pathways involved in the ER stress-induced cell death in the brain were compared between lethargic and control mice. The wet weight of the thalamus in lethargic mouse was lower than that in control mouse. The thalamus has been shown to play an important role in the absence epilepsy. The level of glucose regulated protein (GRP)78, ER chaperons, and activity of c-jun-N-terminal kinase (JNK), phospho-JNK/JNK in the thalamus of lethargic mouse higher than that of control mouse. These data suggested that ER stress was induced in the thalamus in a model of absence epilepsy.In order to elucidate underlying mechanism of cell injury pathways, ER stress (tunicamycine ; TM)- and oxidative stress (H_2O_2 and 4-hydroxy-2-nonenal ; HNE)-induced cell injury pathways were investigated in HT22 cells, a mouse hippocampal cell line. Treatment with TM, H_2O_2 and HNE decreasedthecell viability in a time-and concentration-dependent manner. GADD153/C/EBP homologous protein (CHOP) was significantly induced after exposure to TM. In contrast, expression of caspase-12, ER stress-specific caspase, was not affected by TM. In the cells treated with H_2O_2, significant increases in the immunoreactivities of DJ-1 and nuclear factor-kB (NF-kB) subunits were observed in the nuclear fraction. H2O2 also induced an increase in the intracellular concentration of Ca^<2+> and cobalt chloride, a Ca^<2+> channel inhibitor, suppressed the H_2O_2-induced cell death. In HNE-treated cells, none of these phenomena were observed ; however, HNE adduct proteins were formed after exposure to HNE, but not to H_2O_2.Further experiments are needed to ascertain whether the details of responsible pathways involved in the ER and oxidative stress in absence epilepsy.